Finite element analysis of crowbarring effect during electromagnetic forming

摘要

>Electromagnetic forming (EMF) is a high velocity metal forming technique suitable for Al material due to increase in formability and high electrical conductivity. EMF makes use of only some percentage of the input current pulse passing through the coil generating magnetic force for workpiece deformation while the rest of the pulses are redundant. The damped sinusoidal current can decrease the life of the capacitor. Cutting short the portion of the current pulse which is not responsible for forming is termed as crowbarring. In the case of crowbarring, the reversal current pulses going in the capacitor bank will be reduced and the life of the capacitor bank can be improved significantly. In this paper, FEM studies are carried out to investigate the current crowbarring effect on the technological electromagnetic forming. FEM results are validated with experimental results available in the literature. It has been observed that more number of input current pulses can lead to increased deformation of sheet. However, after 1.5 input current cycles the displacement remained constant. It means that the current pulses after the second current cycle are not contributing to the deformation of the sheet and can be crowbarred.